Description of Prior Art
Heretofore, conversion of liquid hydrocarbons into gels was accomplished by the addition of various gelling or emulsifying agents. These agents fell into one of five distinct classes: (1) the metal soaps, (2) polymers, (3) particulates, (4) the reaction products of amines and organic diisocyanates, or (5) the alkyl-hydroxybutyramides. Aluminum octoate is the most common hydrocarbon gelling agent in current use.
Hydrocarbon gels are used in many applications and may or may not contain suspended particulated solid matter, such as finely divided aluminum. Gels with or without suspended particles are used in incendiary devices, in rocket and jet fuels and in antimisting aviation fuels among other purposes.
Whereas a gel is defined in "The Condensed Chemical Dictionary" as a colloid in which the disperse phase has combined with the continuous phase to produce a viscous jellylike product; a sol is defined there as a "liquid colloidal dispersion". Sols are solutions of various substances in liquids which differ is rheology from gels by being free-flowing.
However, gels and sols as well which incorporate gelling agents of the above listed five types suffer from a number of disadvantages. These include:
(a) the presence of the metal or other inorganic atoms in the gel which can produce residual ash upon combustion that can be detrimental to mechanical parts;
(b) instability after prolonged storage for several years or even months; often resulting in the separation of the liquid hydrocarbon, gelling agent and suspended solids.
(c) some gels are not true gels but viscous liquids and do not have shear-thinning rheology which is required for some known applications for gels.
(d) the above listed gels are formed irreversibly, i.e., they cannot be converted back into a homogeneous liquid once formed.
One example of the problems of current hydrocarbon gels and sols that is easily illustrated is that associated with antimisting fuels. Antimisting fuels are ones that are supposed to not form a mist of very tiny droplets when an airplane crashes. The fine droplets, in the form almost of a vapor, have an extensive surface area and are thus prone to combustion. Therefore it is desired in the field of aviation to reduce the fire hazard of aircraft crashes by suppression of the formation of a fireball by the utilization of antimisting fuel. However, currently used antimisting agents failed in an FAA aircraft crash test. While aluminum -2-ethylhexanoate (aluminum octoate) provides some benefits, according to the Final Summary Report DOT/FAA/CT-86/7 dated Apr. 1986 there is still a need for more effective antimisting agents.